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Waste Management > Lecture 12 - Landfill disposal (chap 10.1-10.2+10.10) > Flashcards

Lecture 12 - Landfill disposal (chap 10.1-10.2+10.10) Flashcards

1
Q

Mention 4 problems concerning landfills around the world.

A
  • 38 of the worlds largest uncontrolled dumpsites are in costal areas, many of them spilling waste directly into the sea.
  • Air pollution from open burning of domestic waste
  • Scavengers/waste pickers (disruptive to operation, safety hazards to scavengers and employees)
  • Landslides
  • Landfill gas (explosive, migration to surroundings, replacement of air, climate burdens).
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2
Q

What are the listed potential impacts from landfills?

A

Greenhouse effects

Ozone depletion (chlorinated and fluorinated hydrocarbons (freons). They originate primarily from solvents, spray cans, insulation foams and compressors.)

Toxic VOCs (The critical compounds are believed to be vinyl chloride and benzene, due to their carcinogenic effects, but also dioxins and furans, formed during incomplete combustion of landfill gas in flares, may be of concern)

Odor (Ammonia, H2S, dimethyl sulfide and mercaptans.)

Noise
Birds, rodents, insects
Litter, dust
Explosion/fire hazard
Vegetation damage
Soil pollution
Surface water pollution

Groundwater pollution (The risk of groundwater pollution is considered to be one of the most important environmental risks at landfills and has led to strict criteria in siting of landfills, and to the installation of liners, leachate collection systems and treatment plants. Ammonia appear to be the most critical component.)

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3
Q

How many EU member states had a landfill ban in 2017?

A

19 member states (9 do not have a ban).

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4
Q

What are the three types of landfill (by technology)?

A
  • Open dump - informal, no treatment
  • Controlled dump - fixed/designated location, no treatment, sometimes temporary covers
  • Sanitary landfills - controlled, gas and leachate treatment, monitoring, covers (with gas flaring, with gas energy recovery, bioreactor landfills.)
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5
Q

What are the 3 types of landfill sites (by type of waste)?

A
  • MSW landfill
  • Industrial landfill
  • Hazardous waste landfill
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6
Q

Which are the primary landfill gases?

A

CH4 and CO2 (is generated by the degradation of the organic waste)

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7
Q

A check list for landfill assessment has been presented in the lecture. List the 5 main topics of this check list.

A
  1. Possibility of land acquisition
    o Land use restriction
    o Land ownership
    o Necessity of compensation
  2. Possibility of getting neighbouring consensus
    o Proximity to settlements
    o “out of sight” measures
    o Need for resettlement
  3. Compatibility with regional development plans
    o Conformity with regional development
    o Direction of urbanization
    o Closeness to airpoirts and flight paths
  4. Technical, Economic and Financial Feasibility
    o Distance from main generation area
    o Area of the site
    o Life expectancy
    o Ease of construction
    o Availability of cover material
    o Estimated land price
    o Estimated cost of compensation for loss of property/land
    o Availability of public services
    o Present conditions of the site (e.g. Soil type, groundwater)
    o Economic value of the site after “aftercare”
  5. Environmental and Socio-Economic acceptability
    o Requirement for resettlement
    o Potential loss of productive land
    o Potential for local employment
    o Impact on religious and recreational uses
    o Impact on water resources
    o Impact on flooding or irrigation
    o Possibility of dust, noise and odour impacts
    o Impact on flora and fauna
    o Traffic impacts
    o Visual and landscape impacts
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8
Q

List types of landfill forms.

A

Closed pit landfill (Trench method)
o Involves the excavation of a trench
o Excavated soil serves as cover material
o Suitable for sites having flat or gently rolling surface, a low groundwater table and a thick soil layer

Area landfill
o Waste is spread and compacted on the surface of the ground
o Cover material is spread and compacted over the layer of waste
o Suitable on flat and gently sloping land and where the groundwater table is high

Landfill cell

Multi barrier concept

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9
Q

List the 4 operational units of landfill sites.

A
  • Landfill gas collection and treatment system
  • Leachate collection and treatment system
  • Rainwater drainage system
  • Environmental monitoring systems
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10
Q

What equipment is a part of the gas collection and treatment on a landfill facility?

A

Top covers, gas wells, pumps, flares and engines/turbines are part of the control of the gas.

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11
Q

The generation of CH4 is dependent on several factors. Which ones?

A
  • precipitation,
  • waste composition,
  • moisture,
  • temperature,
  • landfill depth,
  • availability of nutrients and
  • pH.
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12
Q

Which type of model is the landfill gas generation follworing?

A

First-order decay models

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13
Q

The methane generation potential (Lo) can be expressed with the formula below.
Lo = MCF • DOC • DOCF • F • 16 / 12 (kg CH4/kg waste)

Explain the abbreviations.

A

MCF = Methane correction factor (fraction)
DOC = Degradable organic carbon (Gg C/Gg waste)
DOCF = Fraction of DOC dissimilated (degradable)
F = Fraction by volume of C-CH4 in landfill gas
16 / 12 = Conversion from C to CH4

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14
Q

What equipment is a part of the leachate control on a landfill facility?

A

Top-covers, bottom liners, drainage systems, pumps and treatment plants are part of the leachate control.

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15
Q

Which factors determine the amount of leachate per tonne of waste per year?

A

The depth of the landfill and the bulk density of the waste determine the amount of leachate per tonne of waste per year.

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16
Q

The methane generation potential depends on 4 variable and 1 constant, which?

A

MCF = methane correction factor (fraction, depends on landfill type)
DOC = Degradable organic carbon (Gg C /Gg waste)
DOCF = fraction of DOC dissimilated (degradable)
F = fraction by volume of C-CH4 in landfill gas
16/12=conversion from C to CH4.

17
Q

List some of the treatment options for leachate.

A
  • Biological methods (anaerobic, aerobic, denitrification, nitrification)
  • Physical methods (sedimentation, evaporation)
  • Physical/chemical methods (activated carbon, membrane, resin, ion exchange, flocculation and precipitation)
  • Chemical methods (ozone, hydrogen peroxide, UV rays)
  • Thermal treatment
  • Recirculation
18
Q

Which are the primary landfill gases?

A

CH4 and CO2

19
Q

What are the barriers to be considered when planning and designing landfills?

A
  • Site landfill distant from important groundwater resources and vulnerable surface waters.
  • Site landfills in geological stable strata avoiding physical damage to the landfill body and its installations.
  • Site landfills in geological strata providing subsurface attenuation capacity (e.g not in fractured rock) in case minor leakage should take place.
  • Place the landfills above ground with natural drainage to visible ditches that will reveal inadequate functioning of the leachate collection system.
  • Limit the types of waste accepted at the landfill and/or demand pretreatment of the waste prior to landfilling. Enforce the limitations by inspecting the waste entering the landfill.
  • Install bottom liners and drainage collection systems that are adequately designed, constructed and maintained.
  • Install top covers that are adequately designed, constructed and maintained.
  • Operate the landfill so that the stabilization processes can proceed.
  • Monitor leachate generation and surrounding groundwater to control that the landfill leachate is collected and does not enter the groundwater.
  • Prepare a contingency plan that specifies immediate investigations and possible remediation initiatives if unexpected leachate appearance or behavior is observed.
20
Q

Which treatment options are there for leachate?

A
  • Biological methods (anaerobic, aerobic, denitrification, nitrification)
  • Physical methods (sedimentation, evaporation)
  • Physical/chemical methods (activated carbon, membrane, resin, ion exchange, flocculation and precipitation)
  • Chemical methods (ozone, hydrogen, peroxide, UV rays)
  • Thermal treatment
  • recirculation
21
Q

Which operational units should be on a landfill site?

A
  • Landfill gas collection and treatment system
  • Leachate collection and treatment system
  • Rainwater drainage system
  • Environmental monitoring systems
22
Q

Which to landfill methods/forms have been presented

A
  • Trench method (involves excavation of a trench, soil serves as cover, suitable for sites having flat or rently rolling surface, a low groundwater table and a thick soil layer.)
  • Area method (waste is spread and compacted on the surface of the ground, cover material is spread and compacted over the layer of waste, sutible on flat and gently sloping land and where groundwater table is high).
23
Q

What is a multi-barrier landfill design?

A

There are multiple layers surronding the landfilled waste (eg. soil, drainage layer, vegetation, LLDPE geomembranes etc.)

24
Q

Explain the concept of “final storage quality”

A

The Swiss guideline suggested that a landfill reaches final storage quality when it meets the quality of the surrounding geological strata. This is specified in terms of reaching fluxes of elements so low that they will not significantly alter the surrounding environment.

25
Q

Explain site-specific risk assessment

A

Site-specific risk assessment is the structured and transparent process of identifying and quantifying risks and assessing the significance of these risks in relation to other risks in a specific area with an existing or planned specified landfill.

26
Q

Which 3 steps are included in site-specific risk assessment?

A
  1. Conceptual model: The first step in a site-specific risk assessment often is developing a conceptual model of the proposed landfill and its environmental setting.
  2. Risk screening: The second step in site-specific risk assessment is risk screening (sometimes referred to as Tier 1), which based on assessing the likelihood and the consequences of effects, prioritizes the risks such that any subsequent, more detailed risk assessment can focus on those risks identified as important.
  3. Quantitative risk assessment: The third step is to quantify the critical risks in order to provide a basis for deciding that the risk is acceptable, the landfill should not be accepted, or that acceptance is conditioned, for example, in terms of technical improvements in the design or restrictions in the waste accepted.
27
Q

What are the two types of landfill gas management systems?

A

o Active gas management system:
In an active gas management system, gas is removed from a landfill by the application of suction to a series of wells placed in the landfill. The most common system is based on the extraction from vertical perforated pipes

o Passive gas management system
In a passive system, the gas is vented in the absence of a vacuum extraction system. Passive systems are more typical used at smaller landfills with little gas production and at sites where active systems are not required by regulation.

28
Q

Explain how the gas is extracted in an active gas collection system and also explain the typical use of the gas.

A
  • Active gas collection –> extraction through vertical perforated pipes.
  • Usually a pump or compressor is used for extracting the gas.
  • Pipes are connected to a system of horizontal pipes to convey the gas to a pump station.
  • The gas is either sent to an energy recovery facility or to a flare.
  • The most common use of LFG is in a gas engine that runs an electric generator producing power.
29
Q

Models to predict the amount of Landfill gas (LFG) that can be expected are used in at least three applications. Mention these.

A
  • To determine whether, and at what time, the amount of gas produced will be sufficient to support a beneficial use as described later in this section.
  • To size gas collection systems.
  • For national inventories of CH4 production from landfills for purposes of national greenhouse gas reporting.
30
Q

When are the majority of gas generated in a landfill?

A

first 20 years after disposal.

31
Q

The methane generation in a landfill is affected by several landfill dependent vaiables, which?

A
  • Percipitation
  • Waste composition
  • moisture
  • Temperature
  • landfill depth
  • availability of nutrients
  • pH
32
Q

Which waste fraction has the highest and lowest gas production(l/kg)

A

Highest: biowaste 340 l/kg
lowest: gardening waste 95 (l/kg)

33
Q

Methane generation (m3/yr) can be describe with which model?

A

first-order decay model, depends on:

  • methane generation potential (m3/t)
  • waste landfilled (t/yr)
  • methane generation rate constant (1/yr)
  • time since initial refuse placement (yr)
34
Q

The methane generation potential depends on 4 variable and 1 constant, which?

A

MCF = methane correction factor (fraction)
DOC = Degradable organic carbon (Gg C /Gg waste)
DOCF = fraction of DOC dissimilated (degradeble)
F = fraction by volume og C-CH4 in landfill gas
16/12=conversion from C to CH4.

35
Q

What units are part of leachate control?

A
  • Top covers
  • bottom liners
  • Drainage systems
  • pumps
  • treatment plants
36
Q

What is important factors in leachate generation?

A
  • Percipitation
  • Evaporation
  • Surface runoff
  • Type of operation (waster, water content, layers, capping)
  • depth of landfill
  • bulk density of waste
37
Q

Which compostion parameters are important for the content in the leachate?

A
  • Waste composition and age
  • COD - chemical oxygen demand
  • BOD - biological oxygen demand
  • AOX - Absorbable organic hallides
  • TOC - total organic carbon
  • N2 - Nitrogen (ammonium, nitrite, nitrate)
  • Inorganic substances (salt ions)
  • Heavy metals (mercury, zinc, chromium, cadmium, lead, copper).
38
Q

Which treament options are there for leachate?

A
  • Biological

Waste Management (13 decks)

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